Browsing by Author "Lee, Chih-Hao"

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A Compact 4.4 Tesla Cryogenic Wavelength Shifter for the Taiwan Photon Source
(2017)
Wang, Chao-Chin
;
Chang, Cheng-Hsiang
;
Hwang, Ching-Shiang
;
Lee, Chih-Hao
;
電子物理學系
The feasibility of a compact 4.4 T in-vacuum cryogenic Pr2Fe14B-based wavelength shifter was studied at the Taiwan Photon Source. The overall dimensions of the magnet array are height 205 mm, length 240 mm, and width 160 mm; the magnet array operates at magnet gap 5 mm. The roll-off of the central field on the transverse axis was designed to be less than 0.1% between +/- 20 mm. The magnitudes of the integral multipole field error and the transverse tune shift as a function of transverse position were optimized to be less than 200 G cm and 4 x 10(-3) between +/- 15 mm. A reverse field occurred so that the Pr-Fe-B bulk became partially demagnetized near 295 K, but it was improved upon chamfering the iron poles near the regions of that reverse field to avoid demagnetization of the Pr-Fe-B bulk.
A Compact 4.4 Tesla Cryogenic Wavelength Shifter for the Taiwan Photon Source
(2017)
Wang, Chao-Chin
;
Chang, Cheng-Hsiang
;
Hwang, Ching-Shiang
;
Lee, Chih-Hao
;
電子物理學系
The feasibility of a compact 4.4 T in-vacuum cryogenic Pr2Fe14B-based wavelength shifter was studied at the Taiwan Photon Source. The overall dimensions of the magnet array are height 205 mm, length 240 mm, and width 160 mm; the magnet array operates at magnet gap 5 mm. The roll-off of the central field on the transverse axis was designed to be less than 0.1% between +/- 20 mm. The magnitudes of the integral multipole field error and the transverse tune shift as a function of transverse position were optimized to be less than 200 G cm and 4 x 10(-3) between +/- 15 mm. A reverse field occurred so that the Pr-Fe-B bulk became partially demagnetized near 295 K, but it was improved upon chamfering the iron poles near the regions of that reverse field to avoid demagnetization of the Pr-Fe-B bulk.
Infinite chiral single-helical structures formed by the self-assembly of Cu(II)-N-(2-pyridylmethyl)-aspartate complexes
(2009)
Wu, Shu-Pao
;
Lee, Chih-Hao
;
應用化學系
;
Department of Applied Chemistry
Two crystal structures of [Cu(L-pasp)(H(2)O)] center dot 4H(2)O and [Cu(D-pasp)( H(2)O)] center dot 4H(2)O [pasp = N-(2-pyridylmethyl)-aspartate] were determined using X-ray crystallography and the Cu(II)-pasp complexes were demonstrated to self-assemble through the formation of a Cu-O bond between Cu(II) and the side-chain carboxylate, forming left-handed and right-handed helical coordination polymers, respectively.
Ni-Nanocluster Modified Black TiO2 with Dual Active Sites for Selective Photocatalytic CO2 Reduction
(2018-01-11)
Billo, Tadesse
;
Fu, Fang-Yu
;
Raghunath, Putikam
;
Shown, Indrajit
;
Chen, Wei-Fu
One of the key challenges in artificial photosynthesis is to design a photocatalyst that can bind and activate the CO2 molecule with the smallest possible activation energy and produce selective hydrocarbon products. In this contribution, a combined experimental and computational study on Ni-nanocluster loaded black TiO2 (Ni/TiO2[Vo]) with built-in dual active sites for selective photocatalytic CO2 conversion is reported. The findings reveal that the synergistic effects of deliberately induced Ni nanoclusters and oxygen vacancies provide (1) energetically stable CO2 binding sites with the lowest activation energy (0.08 eV), (2) highly reactive sites, (3) a fast electron transfer pathway, and (4) enhanced light harvesting by lowering the bandgap. The Ni/TiO2[Vo] photocatalyst has demonstrated highly selective and enhanced photocatalytic activity of more than 18 times higher solar fuel production than the commercial TiO2 (P-25). An insight into the mechanisms of interfacial charge transfer and product formation is explored.
Numerical analysis of brilliance and coherent photon flux of segmented undulator radiation based on statistical optics
(2019-01-01)
Luo, Hao-Wen
;
Chung, Ting-Yi
;
Lee, Chih-Hao
;
Hwang, Ching-Shiang
;
電子物理學系
A method based on wave optics together with electron tracking is used to analyze synchrotron radiation from a segmented undulator in a double or multi mini- function lattice storage ring. Radiation brilliance and transverse coherence features are investigated, where the former is calculated with the Wigner distribution function and the latter is evaluated by integrating the photon flux and cross-spectral density to exhibit the coherent flux and overall degree of coherence. To be specific, radiation properties for a single undulator in a typically single mini- function and a tandem undulator in a double mini-(y) lattice are compared in this work. As a result, both, brilliance and coherent flux can be enhanced by a second tandem undulator at the Taiwan Photon Source.
Real-time investigation of the structural evolution of electrodes in a commercial lithium-ion battery containing a V-added LiFePO4 cathode using in-situ neutron powder diffraction
(2013-12-15)
Hu, Chih-Wei
;
Sharma, Neeraj
;
Chiang, Ching-Yu
;
Su, Hui-Chia
;
Peterson, Vanessa K.
In-situ neutron powder diffraction was employed to investigate the structural evolution of the electrode materials in a commercial lithium-ion battery used for electric buses in Taiwan. The battery, containing a vanadium-added LiFePO4 cathode, does not exhibit a delayed phase transition between LiFePO4 (triphylite) and FePO4 (heterosite) suggesting that the delayed phase transition can be suppressed through the use of vanadium-added LiFePO4 cathodes, which also enhances the capacity and prolongs the cycle life of these batteries. Furthermore, we characterize the readily reversible structural change of the anode (LixC6 where 0 < x <= 1) and correlate this to battery voltage. (C) 2013 Elsevier B.V. All rights reserved.
Solution-processable bismuth iodide nanosheets as hole transport layers for organic solar cells
(2014-02-01)
Boopathi, Karunakara Moorthy
;
Raman, Sankar
;
Mohanraman, Rajeshkumar
;
Chou, Fang-Cheng
;
Chen, Yang-Yuang
In this paper we demonstrate the use of low-temperature-solution-processable bismuth iodide (BiI3) nanosheets as hole transport layers in organic photovoltaics with an active layer comprising poly(3-hexylthiophene) (P3HT) mixed with a fullerene derivative. The performance of the resulting devices was comparable with that of corresponding conventionally used systems incorporating polyethylenedioxythiophene:polystyrenesulfonate (PEDOT:PSS). UV-vis spectroscopy revealed that the transparency of a BiI3 layer in the visible ( > 620 nm) and near-infrared range is greater than that of a PEDOT:PSS layer. X-ray photoemission spectroscopy of a BiI3 film revealed signals at 158.8, 164, 618.6, and 630 eV-characteristic of Bi 4f(7/2), Bi 4f(5/2), I 3d(5/2), and I 3d(3/2), respectively-that indicated a stoichiometric BiI3 film. Wet milling of BiI3 crystals resulted in the formation of nanosheets, the presence of which we confirmed using scanning electron microscopy. The resultant power conversion efficiency of the device was approximately 3.5%, with an open-circuit voltage of 0.56 V, a short-circuit current density of 10.4 mA cm(-2), and a fill factor of 60.1% under AM1.5G irradiation (100 mW cm(-2)). (C) 2013 Elsevier B.V. All rights reserved.
The Structures of Yttrium Iron Garnet/Gadolinium Gallium Garnet Superlattice Thin Films Studied by Synchrotron X-Ray Surface Scattering
(2013-07-01)
Lee, Chih-Hao
;
Liang, Keng S.
;
Chern, M. Y.
;
電子物理學系
;
Department of Electrophysics
X-ray measurements (specular and off-specular X-ray reflectivity, in-plane and plane-normal diffraction and truncation rod measurement) were carried out to characterize the epitaxial magnetic multilayers of yttrium iron garnet/gadolinium gallium garnet(GGG) on GGG substrate grown by the laser ablation deposition method. The perfection of the multilayer epitaxy can be better revealed in the observation of the 2(nd) harmonics of superlattice peaks in the reflectivity measurement, the forbidden diffraction peaks and the truncation rod measurement.
Vanadium Substitution of LiFePO4 Cathode Materials To Enhance the Capacity of LiFePO4-Based Lithium-Ion Batteries
(2012-11-22)
Chiang, Ching-Yu
;
Su, Hui-Chia
;
Wu, Pin-Jiun
;
Liu, Heng-Jui
;
Hu, Chih-Wei
The mechanism of enhancing the capacity of the LiFePO4 cathodes in lithium ion batteries by the addition of a small amount of vanadium, which locate on the lithium site and induce lithium vacancies in the crystal structure, is reported in this article. As a result, the capacity increases from 138 mAh/g found for pristine LiFePO4 to 155 mAh/g for the V-added compound, and the conductivity increases from 4.75 x 10(-4) S/cm for the LiFePO4 without V addition to 1.9 x 10(-2) S/cm for the V-added compound. A possible model to facilitate the enhancement of conductivity and capacity is described with evidence supported by X-ray powder diffraction, X-ray absorption spectroscopy, and neutron powder diffraction data.